Mix the all purpose flour, almond flour, kosher salt and powdered sugar in a large bowl. Add the unsalted butter pieces and work into the flour, creating thin sheets of butter in the flour. Mix the egg yolk with 1 tablespoon water in a small bowl and add to the flour and butter mix. Continue to work with your fingers until the mixture sticks together when pinched. Add another tablespoon of water if needed.

Press the dough into a buttered tart pan with a removable bottom (I used a long tart pan but you can use a 10-inch round pan) or 4-6 individual tart pans with removable bottoms. Prick the bottom with a fork and then refrigerate for about an hour.

Preheat the oven to 375 degrees. Bake the tart for 12-15 minutes or until golden brown. Allow to cool completely before filling with mascarpone filling.

For the mascarpone filling

Whip the cream on high with a hand mixer or a stand mixer. Add the softened mascarpone cheese and powdered sugar and beat to mix well. Fold in the lemon curd with a wooden spoon.

In a separate bowl, mix the raspberries and sliced strawberries. Heat the strawberry preserves until thinned and mix into the berries. Spoon the mascarpone into the cooled tart crust and top with the berries. Garnish with mint leaves if desired.